/*
 * 
 * Original author: alpha_lam
 * Creation date: ?
 *
 * Source: $HeadURL$
 * Last changed: $LastChangedDate$
 * 
 * 
 * the unrar licence applies to all junrar source and binary distributions 
 * you are not allowed to use this source to re-create the RAR compression algorithm
 *
 * Here some html entities which can be used for escaping javadoc tags:
 * "&":  "&#038;" or "&amp;"
 * "<":  "&#060;" or "&lt;"
 * ">":  "&#062;" or "&gt;"
 * "@":  "&#064;" 
 */
package com.github.junrar.rarfile;

public class FileNameDecoder
 {
  public static int getChar(byte[] name, int pos)
   {
    return name[pos] & 0xff;
   }

  public static String decode(byte[] name, int encPos)
   {
    int decPos = 0;
    int flags = 0;
    int flagBits = 0;

    int low = 0;
    int high = 0;
    int highByte = getChar(name, encPos++);
    StringBuffer buf = new StringBuffer();
    while (encPos < name.length)
     {
      if (flagBits == 0)
       {
        flags = getChar(name, encPos++);
        flagBits = 8;
       }
      switch (flags >> 6)
       {
       case 0:
        buf.append((char) (getChar(name, encPos++)));
        ++decPos;
        break;
       case 1:
        buf.append((char) (getChar(name, encPos++) + (highByte << 8)));
        ++decPos;
        break;
       case 2:
        low = getChar(name, encPos);
        high = getChar(name, encPos + 1);
        buf.append((char) ((high << 8) + low));
        ++decPos;
        encPos += 2;
        break;
       case 3:
        int length = getChar(name, encPos++);
        if ((length & 0x80) != 0)
         {
          int correction = getChar(name, encPos++);
          for (length = (length & 0x7f) + 2; length > 0 && decPos < name.length; length--, decPos++)
           {
            low = (getChar(name, decPos) + correction) & 0xff;
            buf.append((char) ((highByte << 8) + low));
           }
         }
        else
         {
          for (length += 2; length > 0 && decPos < name.length; length--, decPos++)
           {
            buf.append((char) (getChar(name, decPos)));
           }
         }
        break;
       }
      flags = (flags << 2) & 0xff;
      flagBits -= 2;
     }
    return buf.toString();
   }
 }
